The present invention relates to a substrate cleaning apparatus and method of cleaning both surfaces of a substrate such a semiconductor wafer or an LCD substrate.
In a process for manufacturing semiconductor devices, it is very important to maintain both surfaces of a semiconductor wafer at clean conditions. Therefore, it is necessary to remove contaminants, such as particles, organic substances, and metallic ions, attached to both surfaces of the semiconductor wafer. The contaminants are removed from front and rear surfaces of the semiconductor wafer by using a single-processing apparatus for cleaning both surfaces as disclosed, for example, in U.S. patent application Ser. No. 09/135,478 (filed on Aug. 17, 1998).
In a conventionally used cleaning apparatus 100 shown in FIG. 1, a wafer W is horizontally held by a peripheral holding member 103. While the wafer W is rotated by means of a spin chuck 101, a process liquid is supplied to the center portion of an upper surface (front surface) of the wafer W from an upper nozzle (not shown); at the same time, a process liquid is supplied to the center portion of a lower surface (rear surface) of the wafer W from a lower nozzle 102. However, the process liquid 104 supplied to the lower surface of the wafer W falls down from the wafer W before it reaches to the peripheral portion of the wafer W. As a result, the process liquid 104 may not be supplied to the peripheral portion of the wafer W in a sufficient amount. In addition, the surfaces of the wafer W are hydrophobic, so that the process liquid 104 is likely to be repelled from the lower surface of the wafer W and fall off. It follows that the lower peripheral portion of the wafer W is washed insufficiently. In particular, when a large-sized wafer (e.g., 8 or 12 inch diameter) is used, the process liquid 104 rarely reaches the lower peripheral portion of the wafer W, with the result that the lower peripheral portion is cleaned but incompletely.
In a step of manufacturing a semiconductor device, a silicon oxide film (insulating film) is often formed on the wafer W. The silicon oxide film (insulating film) is, however, an unnecessary film for a non-pattern formation region (rear surface) of the wafer W. The insulating film must be removed from the rear surface of the wafer. However, when the insulating film is tried to remove from the rear surface of the wafer, the pattern formed on the front surface is sometimes damaged.
An object of the present invention is to provide a substrate cleaning apparatus and method capable of supplying a process liquid in a sufficient amount even to a peripheral portion of a rear surface of the substrate, and uniformly cleaning the entire rear surface of the substrate, without damaging an upper surface of the substrate.
According to the present invention, there is provided an apparatus for cleaning the substrate, comprising:
a spin chuck for holding a substrate substantially horizontally;
a rotation driving mechanism for rotating the spin chuck;
a lower nozzle having a plurality of liquid outlet ports facing both a peripheral portion and a center portion of a lower surface of the substrate held by the spin chuck;
a process liquid supply mechanism for supplying a first process liquid to the lower nozzle; and
a controller for controlling operations of the process liquid supply mechanism and the rotation driving mechanism, individually,
in which the controller controls the rotation driving mechanism to rotate the spin chuck and controls the process liquid supply mechanism to supply the first process liquid to the lower nozzle, thereby outputting the first process liquid toward the peripheral portion and the center portion of the lower surface of the substrate.
According to the present invention, there is provided a method of cleaning a substrate comprising the steps of:
(a) holding a substrate rotatably and substantially horizontally;
(b) rotating the substrate; and
(c) supplying a first process liquid from a lower nozzle to both a peripheral portion and a center portion of a lower surface of the substrate held by a spin chick, substantially simultaneously, and supplying a second process liquid from an upper nozzle to an upper surface of the substrate held.
In this case, the second process liquid is pure wafer for protecting the upper surface of the substrate. The first process liquid is an etching solution for dissolving and removing a thin film coated over the lower surface of the substrate. More specifically, the first process liquid is one selected from the group consisting of an ammonia/hydrogen peroxide solution mixture, an hydrochloric acid/hydrogen peroxide solution mixture, and an aqueous hydrofluoric acid solution.
According to the present invention, the first process liquid is supplied from the lower nozzle uniformly to the region extending from the center portion to any peripheral portion of the lower surface of the substrate. It is therefore possible to uniformly dissolve and remove the oxide film from the lower surface of the substrate.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.